A lookup table (LUT) circuit is used in various fields to replace the duplicated calculation circuits. For example, a lookup table circuit is used in many computer related fields, such as computer graphics, image processing and analog or digital video processing, to convert one function to another function.
Typically, in a lookup table application, a table with calculated results of a certain function is stored in a memory first. Next, when executing the function, a LUT circuit is used to search this table to output a result value corresponding to an input value. Such LUT circuit applications may replace duplicated circuit structure to reduce the circuit area.
However, the typical LUT circuit can only search for one stored value at one time. In other words, a searching process has to be performed repeatedly for finding each stored value. The other function execution of the circuit cannot proceed until all corresponding stored values are found in the lookup table. Such a LUT circuit takes much time in the repeated searching process.
Therefore, a LUT circuit that can find more than one stored values at one time is very necessary.